Principia investigated for the Owner the accident of the Aznalcóllar tailings pond and established that the failure was caused by the fact that the designers had not taken into account the slow consolidation of the marls and the brittleness of their behaviour.
The detailed simulation of the accident was rather complex. It required coupled analyses, based on effective stresses throughout the construction period, and the softening behaviour of the marls had to be explicitly modelled. Moreover, the failure triggered the liquefaction of the tailings and a sudden acceleration of the process: the dam underwent displacements of tens of metres along a length of hundreds of metres.
